MT ends after photoablation in vivo. (A) Representative images of MTs and SPR2 before and after laser ablation. Lightning bolts indicate laser ablation position and time. Kymographs illustrate MT and SPR2 dynamics (Fig. S2). A schema of MT laser ablation is shown on the right. The plus and minus signs indicate the MT plus and minus ends, respectively. (B) MT laser ablation in WT and spr2-2. Representative images (top) and kymographs (bottom) of MTs before and after laser ablation (blue lightning bolts) in WT and spr2-2 cells. Yellow dashed lines trace the position of the MT ends in the kymographs. Blue lightning bolts and dotted lines show the times and locations of photoablations. (C) Histograms of the relative frequency of MT end shrinking velocities of the MT ends generated by laser ablation. From top to bottom they show the velocities in plants expressing SPR2-GFP and mCherry-TUA5 (n = 36), mCherry-TUA5 in WT (n = 62), and spr2-2 (n = 69). Note that each ablation generates two shrinking MT ends. The distribution of shrinking speeds after severing are significantly different (P < 0.01, Mann–Whitney U test).